The effect of substituents on magnetic order and superconductivity in RuSr2R2−yCeyCu2O10+δ (R = Eu, Gd)

We have used the partial substitution of Cu by Zn and Ru by Sn to probe the normal, superconducting, and magnetic states in the superconducting and magnetically ordered ruthenocuprate RuSr2R2−yCeyCu2O10+δ (R = Eu, Gd). The effect of Zn substitution for Cu in the CuO2 planes is to suppress the superconducting transition temperature at a rate similar to that observed in other high temperature superconducting cuprates. Sn substitution for Ru rapidly suppresses the temperature where the ferromagnetic component is observed. This suppression rate depends on the Ce content. We observe that the temperature where the bulk Meissner phase commences is closer to the superconducting transition temperature when the ferromagnetic component is completely suppressed. This provides direct support for the spontaneous vortex phase model that has been applied to RuSr2Gd1.4Ce0.6Cu2O10+δ to account for coexisting magnetic and superconducting orders.